This present invention is directed to methods and apparatus for interbody distraction and implant/transplant insertion.
The spine surgical community and surgical literature accept intervertebral devices (commonly known as interbody spacers, and allograft transplants) as part of the art and routine practice in the reconstruction of collapsed intervertebral disc spaces. Surgeons insert these interbody devices/transplants to facilitate bone fusion in between and into the contiguous involved vertebrae. This fusion creates a new solid bone mass, which acts to hold the spinal segment at an appropriate biomechanically restored height as well as to stop motion in a painful segment of the spine. Items surgically placed in these involved interbody regions can thus stimulate interbody bone in-growth such that the operated anterior spinal segments heal into a contiguous bone mass; this means that a fusion occurs. Further, the surgical community uses such man-made implants or biological options to provide weight bearing support between adjacent vertebral bodies, and thereby correct or alleviate a variety of clinical problems. In this regard, surgeons use intervertebral spinal implants/transplants for surgical therapy for degenerative disc disease (DDD), discogenic low back pain, spondylolisthesis, reconstruction following tumor or infection surgery, and other spine related maladies requiring surgical intervention. Herein, a gap separating two adjacent bodies is referred to as an interbody cavity. A gap separating two adjacent vertebral bodies is referred to as an intervertebral cavity.
In many implant designs, a relatively hard or sturdy implant construct is formed from a selected biocompatible material such as metal, ceramic, or carbon fiber-reinforced polymer. This implant construct often has a partially open or porous configuration and is coated or partially filled with a selected bone ingrowth-enhancing substance, such as harvested bone graft supplied from the patient, human donor allograft bone transplant material supplied by a tissue bank, genetically cultivated bone growing protein substitutes, and/or other biological/biochemical bone extenders. Such devices, when implanted into the intervertebral space, promote ingrowth of blood supply and grow active and live bone from the adjacent spinal vertebrae to inter-knit with the implant, thereby eventually immobilizing or fusing the adjacent spinal vertebrae. Such implants also commonly include a patterned exterior surface such as a ribbed or serrated surface, or screw thread geometry, to achieve enhanced mechanical locking with the adjacent vertebrae during the bone ingrowth/fusion process.
The inventory of available surgical devices has expanded to include machined, transplantable allograft bone spacers. Bone Banks and tissue processors are able to precision-engineer donated human bone to specific vertebral interbody milled dimensions most likely to fit into the affected intra-discal zones. For many spine surgeons these biological solutions may prove a better option for a particular patient than the use of man-made materials.
The intervertebral or interbody implants of these general types have achieved a significant degree of clinical success. Notwithstanding this success, a variety of problems arise in connection with surgical interbody implant placement. Surgeons can have difficulty with the implantation process because of individual pathology, deformity, anatomical space restraints, or implant material limitations.
Often, implant placement proves a difficult and time-consuming procedure when the adjacent vertebrae's soft tissue support elements degenerate, causing collapse of the spaces between the vertebrae. This degenerative condition coupled with compromised adjacent tissues, nerves and vasculature may impede physical and visual access to the intervertebral space.
Spine surgery of this type may require removal of the remaining disc material, release of the contracted soft tissues around the disc space, and some degree of distraction or pulling apart of the adjacent vertebrae in an attempt to restore disc space height, realign the spine, and indirectly decompress the nerve roots exiting the spine posteriorly at that level. This distraction procedure has traditionally required the use of several surgical distraction instruments, which may increase the procedure's overall complexity, intensify the invasiveness of the surgical procedure, and possibly lead to iatrogenic vascular and neurosurgical injuries which can cause intraoperative surgical complications. At the same time, use of multiple instruments may limit the surgeon's manual access and clear visualization of the involved intervertebral space.
After the surgeon removes the disc material, he has made a clean aperture in which to place the device. Typically the surgeon grasps the interbody spacer with a special pliers-like tool and places it at the mouth of this opening. At this juncture, the surgeon typically uses extreme force as he hammers on the top part of the tool so that the implant finds its final placement. This hammering technique vectors enormous shear forces through the spacer. The actual implants have material and engineering limitations which may cause the implant to fracture, shear, or break apart as a result of these forceful insertion moments. In addition, some implant designs require materials which do not tolerate well the use of impaction-type forces necessary to advance the implant into the intervertebral space.
A variety of intervertebral implant insertion instruments have been developed in recent years as a result of efforts to simplify surgical distraction of the intervertebral space while facilitating placement of the implant therein. See, for example, U.S. Pat. Nos. 6,755,841; 6,478,800; and 6,652,533; and U.S. Publication No. 2005/0165408 which disclose instruments for advancing an intervertebral implant between a pair of pivotally mounted distraction levers used to engage and distract adjacent vertebral structures. In these designs, the advancing movement of the implant is accompanied by wedged separation of the distal end tips of the levers which are engaged with and thereby separate or distract the adjacent vertebral structures.
While such implant insertion instruments provide a significant improvement in the art, the implant is not always safeguarded against substantial and potentially undesirable compression and shear forces during such advancing displacement between the pivoting distraction levers. In addition, these instruments have not provided a simple mechanism for quickly and easily retracting the distal end tips of the levers from the distraction space following intervertebral placement of the implant. Moreover, these instruments have not provided or contemplated the capability for use with implants of different sizes, such as implants having different height dimensions which may be indicated by specific patient requirements, without altering the insertion angle of the distal end tips of the distraction levers. In this regard, an amplified increase in the tip insertion angle, associated with implantation of a significantly taller implant, can undesirably increase the complexity and difficulty of the surgical implantation procedure.
There exists, therefore, a significant need for further improvements in and to intervertebral implant insertion instruments and related intervertebral implants for use therewith, particularly with respect to quickly and easily distracting the intervertebral space for facilitated placement of an implant having a range of different heights, for safeguarding the implant against compression and shear forces during intervertebral distraction, and further for quickly and easily releasing the implant from the insertion instrument within the intervertebral space.